/*
 *    Copyright 2009-2022 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       https://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.mybatis.guice;

import java.util.Collection;
import java.util.NoSuchElementException;

/**
 * Simple static methods to be called at the start of your own methods to verify correct arguments and state. This
 * allows constructs such as
 *
 * <pre>
 * if (count <= 0) {
 *   throw new IllegalArgumentException("must be positive: " + count);
 * }
 * </pre>
 * <p>
 * to be replaced with the more compact
 * </p>
 *
 * <pre>
 * checkArgument(count > 0, "must be positive: %s", count);
 * </pre>
 * <p>
 * Note that the sense of the expression is inverted; with {@code Preconditions} you declare what you expect to be
 * <i>true</i>, just as you do with an <a href="http://java.sun.com/j2se/1.5.0/docs/guide/language/assert.html">
 * {@code assert}</a> or a JUnit {@code assertTrue()} call.
 * </p>
 * <p>
 * Take care not to confuse precondition checking with other similar types of checks! Precondition exceptions --
 * including those provided here, but also {@link IndexOutOfBoundsException}, {@link NoSuchElementException},
 * {@link UnsupportedOperationException} and others -- are used to signal that the <i>calling method</i> has made an
 * error. This tells the caller that it should not have invoked the method when it did, with the arguments it did, or
 * perhaps <i>ever</i>. Postcondition or other invariant failures should not throw these types of exceptions.
 * </p>
 * <p>
 * <b>Note:</b> The methods of the {@code Preconditions} class are highly unusual in one way: they are <i>supposed
 * to</i> throw exceptions, and promise in their specifications to do so even when given perfectly valid input. That is,
 * {@code null} is a valid parameter to the method {@link #checkNotNull(Object)} -- and technically this parameter could
 * be even marked as {@link com.google.inject.internal.util.Nullable} -- yet the method will still throw an exception
 * anyway, because that's what its contract says to do.
 * </p>
 * <p>
 * This class may be used with the Google Web Toolkit (GWT).
 * </p>
 *
 * @author Kevin Bourrillion
 */
final class Preconditions {
  private Preconditions() {
  }

  /**
   * Ensures the truth of an expression involving one or more parameters to the calling method.
   *
   * @param expression
   *          a boolean expression
   *
   * @throws IllegalArgumentException
   *           if {@code expression} is false
   */
  public static void checkArgument(boolean expression) {
    if (!expression) {
      throw new IllegalArgumentException();
    }
  }

  /**
   * Ensures the truth of an expression involving one or more parameters to the calling method.
   *
   * @param expression
   *          a boolean expression
   * @param errorMessage
   *          the exception message to use if the check fails; will be converted to a string using
   *          {@link String#valueOf(Object)}
   *
   * @throws IllegalArgumentException
   *           if {@code expression} is false
   */
  public static void checkArgument(boolean expression, Object errorMessage) {
    if (!expression) {
      throw new IllegalArgumentException(String.valueOf(errorMessage));
    }
  }

  /**
   * Ensures the truth of an expression involving one or more parameters to the calling method.
   *
   * @param expression
   *          a boolean expression
   * @param errorMessageTemplate
   *          a template for the exception message should the check fail. The message is formed by replacing each
   *          {@code %s} placeholder in the template with an argument. These are matched by position - the first
   *          {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted
   *          message in square braces. Unmatched placeholders will be left as-is.
   * @param errorMessageArgs
   *          the arguments to be substituted into the message template. Arguments are converted to strings using
   *          {@link String#valueOf(Object)}.
   *
   * @throws IllegalArgumentException
   *           if {@code expression} is false
   * @throws NullPointerException
   *           if the check fails and either {@code
   *     errorMessageTemplate} or {@code errorMessageArgs} is null (don't let this happen)
   */
  public static void checkArgument(boolean expression, String errorMessageTemplate, Object... errorMessageArgs) {
    if (!expression) {
      throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
    }
  }

  /**
   * Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to
   * the calling method.
   *
   * @param expression
   *          a boolean expression
   *
   * @throws IllegalStateException
   *           if {@code expression} is false
   */
  public static void checkState(boolean expression) {
    if (!expression) {
      throw new IllegalStateException();
    }
  }

  /**
   * Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to
   * the calling method.
   *
   * @param expression
   *          a boolean expression
   * @param errorMessage
   *          the exception message to use if the check fails; will be converted to a string using
   *          {@link String#valueOf(Object)}
   *
   * @throws IllegalStateException
   *           if {@code expression} is false
   */
  public static void checkState(boolean expression, Object errorMessage) {
    if (!expression) {
      throw new IllegalStateException(String.valueOf(errorMessage));
    }
  }

  /**
   * Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to
   * the calling method.
   *
   * @param expression
   *          a boolean expression
   * @param errorMessageTemplate
   *          a template for the exception message should the check fail. The message is formed by replacing each
   *          {@code %s} placeholder in the template with an argument. These are matched by position - the first
   *          {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted
   *          message in square braces. Unmatched placeholders will be left as-is.
   * @param errorMessageArgs
   *          the arguments to be substituted into the message template. Arguments are converted to strings using
   *          {@link String#valueOf(Object)}.
   *
   * @throws IllegalStateException
   *           if {@code expression} is false
   * @throws NullPointerException
   *           if the check fails and either {@code
   *     errorMessageTemplate} or {@code errorMessageArgs} is null (don't let this happen)
   */
  public static void checkState(boolean expression, String errorMessageTemplate, Object... errorMessageArgs) {
    if (!expression) {
      throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
    }
  }

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference
   *          an object reference
   *
   * @return the non-null reference that was validated
   *
   * @throws NullPointerException
   *           if {@code reference} is null
   */
  public static <T> T checkNotNull(T reference) {
    if (reference == null) {
      throw new NullPointerException();
    }
    return reference;
  }

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference
   *          an object reference
   * @param errorMessage
   *          the exception message to use if the check fails; will be converted to a string using
   *          {@link String#valueOf(Object)}
   *
   * @return the non-null reference that was validated
   *
   * @throws NullPointerException
   *           if {@code reference} is null
   */
  public static <T> T checkNotNull(T reference, Object errorMessage) {
    if (reference == null) {
      throw new NullPointerException(String.valueOf(errorMessage));
    }
    return reference;
  }

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference
   *          an object reference
   * @param errorMessageTemplate
   *          a template for the exception message should the check fail. The message is formed by replacing each
   *          {@code %s} placeholder in the template with an argument. These are matched by position - the first
   *          {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted
   *          message in square braces. Unmatched placeholders will be left as-is.
   * @param errorMessageArgs
   *          the arguments to be substituted into the message template. Arguments are converted to strings using
   *          {@link String#valueOf(Object)}.
   *
   * @return the non-null reference that was validated
   *
   * @throws NullPointerException
   *           if {@code reference} is null
   */
  public static <T> T checkNotNull(T reference, String errorMessageTemplate, Object... errorMessageArgs) {
    if (reference == null) {
      // If either of these parameters is null, the right thing happens anyway
      throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
    }
    return reference;
  }

  /**
   * Ensures that an {@code Iterable} object passed as a parameter to the calling method is not null and contains no
   * null elements.
   *
   * @param iterable
   *          the iterable to check the contents of
   *
   * @return the non-null {@code iterable} reference just validated
   *
   * @throws NullPointerException
   *           if {@code iterable} is null or contains at least one null element
   */
  public static <T extends Iterable<?>> T checkContentsNotNull(T iterable) {
    if (containsOrIsNull(iterable)) {
      throw new NullPointerException();
    }
    return iterable;
  }

  /**
   * Ensures that an {@code Iterable} object passed as a parameter to the calling method is not null and contains no
   * null elements.
   *
   * @param iterable
   *          the iterable to check the contents of
   * @param errorMessage
   *          the exception message to use if the check fails; will be converted to a string using
   *          {@link String#valueOf(Object)}
   *
   * @return the non-null {@code iterable} reference just validated
   *
   * @throws NullPointerException
   *           if {@code iterable} is null or contains at least one null element
   */
  public static <T extends Iterable<?>> T checkContentsNotNull(T iterable, Object errorMessage) {
    if (containsOrIsNull(iterable)) {
      throw new NullPointerException(String.valueOf(errorMessage));
    }
    return iterable;
  }

  /**
   * Ensures that an {@code Iterable} object passed as a parameter to the calling method is not null and contains no
   * null elements.
   *
   * @param iterable
   *          the iterable to check the contents of
   * @param errorMessageTemplate
   *          a template for the exception message should the check fail. The message is formed by replacing each
   *          {@code %s} placeholder in the template with an argument. These are matched by position - the first
   *          {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted
   *          message in square braces. Unmatched placeholders will be left as-is.
   * @param errorMessageArgs
   *          the arguments to be substituted into the message template. Arguments are converted to strings using
   *          {@link String#valueOf(Object)}.
   *
   * @return the non-null {@code iterable} reference just validated
   *
   * @throws NullPointerException
   *           if {@code iterable} is null or contains at least one null element
   */
  public static <T extends Iterable<?>> T checkContentsNotNull(T iterable, String errorMessageTemplate,
      Object... errorMessageArgs) {
    if (containsOrIsNull(iterable)) {
      throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
    }
    return iterable;
  }

  private static boolean containsOrIsNull(Iterable<?> iterable) {
    if (iterable == null) {
      return true;
    }

    if (iterable instanceof Collection) {
      Collection<?> collection = (Collection<?>) iterable;
      try {
        return collection.contains(null);
      } catch (NullPointerException e) {
        // A NPE implies that the collection doesn't contain null.
        return false;
      }
    } else {
      for (Object element : iterable) {
        if (element == null) {
          return true;
        }
      }
      return false;
    }
  }

  /**
   * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size {@code size}. An
   * element index may range from zero, inclusive, to {@code size}, exclusive.
   *
   * @param index
   *          a user-supplied index identifying an element of an array, list or string
   * @param size
   *          the size of that array, list or string
   *
   * @throws IndexOutOfBoundsException
   *           if {@code index} is negative or is not less than {@code size}
   * @throws IllegalArgumentException
   *           if {@code size} is negative
   */
  public static void checkElementIndex(int index, int size) {
    checkElementIndex(index, size, "index");
  }

  /**
   * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size {@code size}. An
   * element index may range from zero, inclusive, to {@code size}, exclusive.
   *
   * @param index
   *          a user-supplied index identifying an element of an array, list or string
   * @param size
   *          the size of that array, list or string
   * @param desc
   *          the text to use to describe this index in an error message
   *
   * @throws IndexOutOfBoundsException
   *           if {@code index} is negative or is not less than {@code size}
   * @throws IllegalArgumentException
   *           if {@code size} is negative
   */
  public static void checkElementIndex(int index, int size, String desc) {
    checkArgument(size >= 0, "negative size: %s", size);
    if (index < 0) {
      throw new IndexOutOfBoundsException(format("%s (%s) must not be negative", desc, index));
    }
    if (index >= size) {
      throw new IndexOutOfBoundsException(format("%s (%s) must be less than size (%s)", desc, index, size));
    }
  }

  /**
   * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of size {@code size}. A
   * position index may range from zero to {@code size}, inclusive.
   *
   * @param index
   *          a user-supplied index identifying a position in an array, list or string
   * @param size
   *          the size of that array, list or string
   *
   * @throws IndexOutOfBoundsException
   *           if {@code index} is negative or is greater than {@code size}
   * @throws IllegalArgumentException
   *           if {@code size} is negative
   */
  public static void checkPositionIndex(int index, int size) {
    checkPositionIndex(index, size, "index");
  }

  /**
   * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of size {@code size}. A
   * position index may range from zero to {@code size}, inclusive.
   *
   * @param index
   *          a user-supplied index identifying a position in an array, list or string
   * @param size
   *          the size of that array, list or string
   * @param desc
   *          the text to use to describe this index in an error message
   *
   * @throws IndexOutOfBoundsException
   *           if {@code index} is negative or is greater than {@code size}
   * @throws IllegalArgumentException
   *           if {@code size} is negative
   */
  public static void checkPositionIndex(int index, int size, String desc) {
    checkArgument(size >= 0, "negative size: %s", size);
    if (index < 0) {
      throw new IndexOutOfBoundsException(format("%s (%s) must not be negative", desc, index));
    }
    if (index > size) {
      throw new IndexOutOfBoundsException(format("%s (%s) must not be greater than size (%s)", desc, index, size));
    }
  }

  /**
   * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in an array, list or string of size
   * {@code size}, and are in order. A position index may range from zero to {@code size}, inclusive.
   *
   * @param start
   *          a user-supplied index identifying a starting position in an array, list or string
   * @param end
   *          a user-supplied index identifying a ending position in an array, list or string
   * @param size
   *          the size of that array, list or string
   *
   * @throws IndexOutOfBoundsException
   *           if either index is negative or is greater than {@code size}, or if {@code end} is less than {@code start}
   * @throws IllegalArgumentException
   *           if {@code size} is negative
   */
  public static void checkPositionIndexes(int start, int end, int size) {
    checkPositionIndex(start, size, "start index");
    checkPositionIndex(end, size, "end index");
    if (end < start) {
      throw new IndexOutOfBoundsException(format("end index (%s) must not be less than start index (%s)", end, start));
    }
  }

  /**
   * Substitutes each {@code %s} in {@code template} with an argument. These are matched by position - the first
   * {@code %s} gets {@code args[0]}, etc. If there are more arguments than placeholders, the unmatched arguments will
   * be appended to the end of the formatted message in square braces.
   *
   * @param template
   *          a non-null string containing 0 or more {@code %s} placeholders.
   * @param args
   *          the arguments to be substituted into the message template. Arguments are converted to strings using
   *          {@link String#valueOf(Object)}. Arguments can be null.
   */
  // VisibleForTesting
  static String format(String template, Object... args) {
    // start substituting the arguments into the '%s' placeholders
    StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
    int templateStart = 0;
    int i = 0;
    while (i < args.length) {
      int placeholderStart = template.indexOf("%s", templateStart);
      if (placeholderStart == -1) {
        break;
      }
      builder.append(template.substring(templateStart, placeholderStart));
      builder.append(args[i++]);
      templateStart = placeholderStart + 2;
    }
    builder.append(template.substring(templateStart));

    // if we run out of placeholders, append the extra args in square braces
    if (i < args.length) {
      builder.append(" [");
      builder.append(args[i++]);
      while (i < args.length) {
        builder.append(", ");
        builder.append(args[i++]);
      }
      builder.append("]");
    }

    return builder.toString();
  }
}
